Throughout the 1990s, Reilly's popularity grew with a series of hefty supporting parts, including a role in What's Eating Gilbert Grape (1993). But it was his work in director Paul Thomas Anderson's Hard Eight (1996) that helped Reilly make the transition to leading actor. He and Anderson continued their successful partnership in Boogie Nights (1997) and Magnolia (1999).
In 2002, Reilly appeared in four high-profile films: The Good Girl, The Hours, Gangs of New York and Chicago, which earned him Oscar and Golden Globe nominations for Best Supporting Actor. Reilly continues to balance leading roles, such as his part in Criminal (2004), with memorable supporting turns in films such as The Aviator (2004).